CN100455555C - Purification method of 1,1-difluoroethane - Google Patents

Abstract

Crude 1,1-difluoroethane containing at least one compound selected from the group consisting of unsaturated compounds each having two carbon atoms within the molecule and saturated chlorine-containing compounds each having two carbon atoms within the molecule is brought into contact with a zeolite and/or a carbonaceous adsorbent, or crude 1,1-difluoroethane containing hydrogen fluoride and, as impurities, at least one compound selected from the group consisting of unsaturated compounds each having two carbon atoms within the molecule is brought into contact with a fluorination catalyst in a gas phase state. High-purity 1,1-difluoroethane usable as a cryogenic refrigerant, or as an etching gas, can be produced in an industrially advantageous manner.

Description

The purification method of 1,1-difluoroethane

technical field

The present invention relates to a purification method, production method and use of 1,1-difluoroethane.

Background technique

1,1-Difluoroethane (CH ₃ CHF ₂ ) has attracted attention as, for example, a cryogenic refrigerant or an etching gas.

For the production and purification methods of 1,1-difluoroethane, the following methods are generally employed, such as (1) a method of reducing chlorinated fluorinated hydrocarbons with hydrogen in the presence of a catalyst (see Japanese Unexamined Patent Publication No. 7 -126197 (JP-A-7-126197)), and (2) reacting chlorine in the gas phase by using a fluorination catalyst and reacting unsaturated compounds contained as impurities with oxides of copper, cobalt, silver, magnesium, etc. Methods for fluorination of ethylene (CH ₂ =CHCl), 1-chloro-1-fluoroethane, etc. (see European Unexamined Patent Publication No. 0370688).

For example, CH ₃ CHF ₂ (HFC-152a) produced by the method of reacting 1,1-dichloroethane with hydrogen fluoride in the presence of a fluorination catalyst (general production method) or the above method (1) contains various impurities such as Saturated compounds Hydrocarbons (HC), Hydrochlorocarbons (HCC), Chlorofluorocarbons (CFC), Hydrochlorofluorocarbons (HCFC) and Hydrofluorocarbons (HFC) or unsaturated compounds.

In order to obtain high-purity CH ₃ CHF ₂ , these impurities must be removed as much as possible. In particular, even when it is difficult to separate by normal distillation, chlorine-containing compounds such as hydrochlorocarbons, chlorofluorocarbons, and HCFCs must be purified to increase purity, not only for obtaining high-purity products but also for preventing ozone layer aspects of loss. Among these impurities, some compounds form azeotrope or azeotrope-like mixture with CH ₃ CHF ₂ , and therefore, their separation from CH ₃ CHF ₂ is very difficult.

For example, for the purification of impurities such as 1,1,1,2-tetrafluoroethane (CF ₃ CH ₂ F) and pentafluoroethane (CF ₃ CHF ₂ ), which are important refrigerants, by Purification methods for removing these compounds by extractive distillation or by dehalogenation hydrogenation using hydrogen in the presence of a catalyst are known. However, the purification method by extractive distillation requires many expensive facilities such as distillation towers, which disadvantageously results in high equipment costs and the like. Also, the purification method using hydrogen has problems such as high equipment cost and short catalyst life due to use of combustibles. In addition, hydrogen chloride is generated, and thus, the lifetime of the catalyst is shortened.

To purify 1,1-difluoroethane, for example, the method of (2) above has been suggested, but in the method of (2), a step of removing oxidation products is necessary.

Contents of the invention

Under these circumstances, it is an object of the present invention to provide an industrially advantageous process for producing high-purity 1,1-difluoroethane useful as a cryogenic refrigerant or etching gas.

[How to solve the problem]

After intensive investigations to solve the above-mentioned problems, the present inventors found that the above-mentioned objects can be achieved by using a method that contains Crude 1,1-difluoroethane containing at least one compound of saturated chlorine-containing compounds having two carbon atoms therein and comprising zeolites having an average pore diameter of 3-6 Angstroms and a silica/alumina ratio of ≤ 2.0 and/or or carbonaceous adsorbent having an average pore size of 3.5-6 Angstroms to reduce the amount of this compound contained as an impurity in the crude 1,1-difluoroethane. Based on this finding, the present invention has been accomplished.

The inventors of the present invention have also found that the above object can be achieved by using a method of making crude oil containing hydrogen fluoride and at least one compound selected from unsaturated compounds each having two carbon atoms in the molecule as impurities. 1,1-Difluoroethane is contacted with the fluorination catalyst in a gas phase state to reduce the content of unsaturated compounds each having two carbon atoms in the molecule. Based on this finding, the present invention has been accomplished.

Accordingly, the present invention provides the purification method, production method and use of 1,1-difluoroethane described in [1] to [19] below.

[1] A method of purifying 1,1-difluoroethane, which comprises making a compound selected from unsaturated compounds each having two carbon atoms in the molecule and saturated chlorine-containing compounds each having two carbon atoms in the molecule Crude 1,1-difluoroethane comprising at least one compound in the zeolite having an average pore diameter of 3-6 angstroms and a silica/alumina ratio of ≤ 2.0 and/or carbonaceous having an average pore diameter of 3.5-6 angstroms Adsorbent contacting of the adsorbent to reduce the amount of this compound contained as an impurity in the crude 1,1-difluoroethane.

[2] The method for purifying 1,1-difluoroethane as described in the above item [1], wherein the unsaturated compound having two carbon atoms in the molecule is at least one selected from the group consisting of ethylene, vinyl fluoride, Compounds in vinyl chloride and vinylidene chloride.

[3] The method for purifying 1,1-difluoroethane as described in the above item [1], wherein the saturated chlorine-containing compound having two carbon atoms in the molecule is at least one selected from dichloroethane , 1-chloro-1-fluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane.

[4] The method for purifying 1,1-difluoroethane as described in any one of the above items [1]-[3], wherein the compound contained as an impurity in crude 1,1-difluoroethane The total content is equal to or lower than 0.1% by volume.

[5] The method for purifying 1,1-difluoroethane as described in any one of the above items [1]-[4], wherein the pressure at which crude 1,1-difluoroethane contacts the adsorbent is equal to Or lower than 1MPa.

[6] The method for purifying 1,1-difluoroethane as described in any one of the above items [1]-[5], wherein the purified 1,1-difluoroethane contains as an impurity The total content of the compound is equal to or less than 100vol ppm.

[7] The method for purifying 1,1-difluoroethane as described in any one of the above [1]-[6], wherein each of the The total content of unsaturated compounds having two carbon atoms in the molecule is equal to or less than 50 vol ppm.

[8] The method for purifying 1,1-difluoroethane as described in any one of the above [1]-[7], wherein each of the The total content of saturated chlorine-containing compounds having two carbon atoms in the molecule is equal to or less than 50 vol ppm.

[9] The method for purifying 1,1-difluoroethane as described in any one of the above [1]-[8], wherein crude 1,1-difluoroethane is obtained by comprising the following steps (1)-( 3) method to obtain:

(1) reacting 1,1-dichloroethane with hydrogen fluoride in the presence of a fluorination catalyst to obtain mainly 1,1-difluoroethane,

(2) Separation of hydrogen fluoride, 1,1-dichloroethane and 1-chloro-1-fluoroethane and the separated compounds from the product containing 1,1-difluoroethane obtained in step (1) loop into the reaction step, and

(3) Hydrogen chloride and/or 1,1-difluoroethane are separated by distillation from the 1,1-difluoroethane-containing product obtained in step (1).

[10] 1,1-difluoroethane product, which is 1,1-difluoroethane purified by the method as described in any one of [1]-[9] above, wherein the water content Equal to or lower than 5vol ppm.

[11] 1,1-difluoroethane product, which is 1,1-difluoroethane purified by the method as described in any one of [1]-[9] above, wherein the hydrogen fluoride content Equal to or lower than 2vol ppm.

[12] A refrigerant comprising the 1,1-difluoroethane product described in [10] or [11].

[13] An etching gas comprising the 1,1-difluoroethane product described in [10] or [11].

[14] A method of purifying 1,1-difluoroethane comprising making crude 1 containing hydrogen fluoride and at least one compound selected from unsaturated compounds each having two carbon atoms in the molecule as impurities, 1-Difluoroethane is contacted with the fluorination catalyst in a gas phase state to reduce the content of unsaturated compounds each having two carbon atoms in the molecule.

[15] The method for purifying 1,1-difluoroethane as described in the above item [14], wherein the unsaturated compound having two carbon atoms in the molecule is selected from the group consisting of ethylene, fluoroethylene, chlorofluoroethylene, Vinyl chloride and vinylidene chloride.

[16] The method for purifying 1,1-difluoroethane as described in the above item [14] or [15], wherein each contained as impurities in crude 1,1-difluoroethane is intramolecularly The total content of unsaturated compounds having two carbon atoms is equal to or less than 1% by volume.

[17] The method for purifying 1,1-difluoroethane as described in any one of the above [14]-[16], wherein the fluorination catalyst contains at least one selected from Cu, Mg, Zn, Pb , Cr, Al, In, Bi, Co and Ni, the contact temperature is 100-350°C.

[18] A method for producing 1,1-difluoroethane, comprising the steps of:

(1) reacting 1,1-dichloroethane with hydrogen fluoride in the presence of a fluorination catalyst to obtain a product mainly containing 1,1-difluoroethane,

(2) The product mainly containing 1,1-difluoroethane obtained in step (1) is introduced into the first distillation column, and hydrogen chloride is mainly separated from the top, and the product mainly containing 1,1-difluoroethane is separated from the middle. a side draw containing a small amount of hydrogen fluoride, separating mainly hydrogen fluoride, 1,1-dichloroethane and 1-chloro-1-fluoroethane from the bottom, and recycling the bottom product to the reaction step, and

(3) The side draw (crude 1,1-difluoroethane) obtained in step (2) is brought into contact with a fluorination catalyst in a gas phase state.

[19] A method for producing 1,1-difluoroethane, the method comprising the steps of:

(1) reacting 1,1-dichloroethane with hydrogen fluoride in the presence of a fluorination catalyst to obtain a product mainly containing 1,1-difluoroethane,

(2) The product mainly containing 1,1-difluoroethane obtained in step (1) is introduced into the first distillation column, hydrogen chloride is mainly separated from the top, and hydrogen fluoride, 1,1-difluoroethane are mainly separated from the bottom Fluoroethane, 1,1-dichloroethane and 1-chloro-1-fluoroethane,

(3) The bottom fraction obtained in step (2) is introduced into the second distillation column, and crude 1,1-difluoroethane mainly containing hydrogen fluoride is separated from the top, and hydrogen fluoride, 1,1-difluoroethane are mainly separated from the bottom. Dichloroethane and 1-chloro-1-fluoroethane, and recycling the bottom product to the reaction step,

(4) bringing crude 1,1-difluoroethane mainly containing hydrogen fluoride belonging to the overhead fraction obtained in step (3) into contact with a fluorination catalyst in a gas phase state, and

(5) Hydrogen fluoride is recovered from the reactant obtained in step (4).

According to the present invention, high-purity 1,1-difluoroethane can be efficiently produced by a simple and easy method, and the resulting purified 1,1-difluoroethane can be used as a cryogenic refrigerant or etching gas.

Detailed ways

Preferred embodiments of the present invention are described in detail below.

As described above, regarding the production methods of _{CH3CHF2 ,} for example, (1) a method of reducing chlorinated fluorinated hydrocarbons with hydrogen in the presence of a catalyst, and (2) fluorination of 1 in a gas phase by using a fluorination catalyst, Methods for 1-dichloroethane, 1-chloro-1-fluoroethane, etc. are known. In CH ₃ CHF ₂ produced by these methods, impurities that are difficult to separate from CH ₃ CHF ₂ are contained even when common operations for purification such as distillation are performed. Examples of such impurities include saturated hydrocarbons (HC), hydrochlorocarbons (HCC), chlorofluorocarbons (CFC), hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFC) or unsaturated compounds. These impurities must be removed as much as possible to obtain high purity products.

The method for purifying 1,1-difluoroethane of the present invention is characterized in that: making a compound selected from unsaturated compounds each having two carbon atoms in the molecule and saturated chlorine-containing compounds each having two carbon atoms in the molecule Crude 1,1-difluoroethane comprising at least one compound in the zeolite having an average pore diameter of 3-6 angstroms and a silica/alumina ratio of ≤ 2.0 and/or carbonaceous having an average pore diameter of 3.5-6 angstroms Adsorbent contacting of the adsorbent to reduce the amount of this compound contained as an impurity in the crude 1,1-difluoroethane.

Examples of unsaturated compounds each having two carbon atoms in the molecule contained as impurities in crude 1,1-difluoroethane include at least one kind selected from ethylene, vinyl fluoride, vinyl chloride, and vinylidene chloride. compound. Examples of saturated chlorine-containing compounds each having two carbon atoms in the molecule include at least one selected from dichloroethane, 1-chloro-1-fluoroethane and 2-chloro-1,1,1,2-tetra Compounds in fluoroethane. Crude 1,1-difluoroethane containing these impurities is difficult to purify only by known distillation operations, and the present inventors conducted further studies, for example, by changing the type of adsorbent or the adsorption conditions according to the polarity and pore size of the adsorbent .

As a result, it has been found that the above-mentioned impurities can be selectively adsorbed and removed by bringing them into contact with a zeolite having an average pore diameter of 3-6 angstroms and a silica/alumina ratio (Si/Al ratio) of ≤ 2.0. Even when the silica/alumina ratio is ≤ 2.0, if the average pore size of the zeolite is less than 3 angstroms or exceeds 6 angstroms, the effect of reducing impurities will not be obtained. Also, even when the average pore diameter is 3-6 angstroms, if the silica/alumina ratio of the zeolite exceeds 2.0, the effect of reducing impurities cannot be obtained.

It was also found that the above-mentioned impurities can be selectively adsorbed and removed by contacting these impurities with a carbonaceous adsorbent having an average pore diameter of 3.5-6 angstroms (for example, molecular sieving carbon). If the carbonaceous adsorbent used has an average pore diameter of less than 3.5 angstroms or more than 6 angstroms, the effect of reducing impurities will not be obtained. For example, commonly used activated carbon having an average pore diameter of about 35 angstroms is known to have a strong adsorption capacity, but it cannot provide the effect of reducing these impurities.

The above-mentioned zeolite and carbonaceous adsorbent may be used alone, or both may be used in combination in any ratio.

The total content of these impurities contained as impurities in the crude 1,1-difluoroethane is preferably ≦0.1% by volume, more preferably 0.05% by volume. If the impurity content exceeds 0.1% by volume, the amount of the adsorbent is increased to disadvantageously cause a loss of 1,1-difluoroethane or an increase in equipment cost or the like.

In the purification method of 1,1-difluoroethane of the present invention, the method for bringing crude 1,1-difluoroethane containing these impurities into contact with an adsorbent is not particularly limited, for example, they may be in the gas phase neutral or in the liquid phase, but the method of contacting in the liquid phase is effective and preferred. In order to bring them into contact in a liquid phase, a known method such as a batch system or a continuous system can be employed. For example, a method may be employed in which two fixed-bed system adsorption tower units are provided, and when one adsorption tower reaches saturated adsorption, the tower is switched and regenerated. The pressure for bringing the crude 1,1-difluoroethane into contact with the adsorbent is preferably equal to or less than 1 MPa. If the pressure exceeds 1 MPa, the equipment cost increases, which is not preferable.

In 1,1,-difluoroethane obtained by treating and purifying crude 1,1-difluoroethane as described above, the total content of compounds contained as impurities is ≤ 100 vol ppm, therefore, high purity can be obtained product. The total content of unsaturated compounds each having two carbon atoms in the molecule contained in the purified 1,1-difluoroethane is ≤ 50 vol ppm, and in the purified 1,1-difluoroethane The total content of saturated chlorine-containing compounds each having two carbon atoms in the molecule is also ≦50 volppm. In other words, the purity of the purified 1,1-difluoroethane is ≧99.99% by volume.

Crude 1,1-difluoroethane is preferably crude 1,1-difluoroethane obtained by a process comprising the following steps:

(1) reacting 1,1-dichloroethane with hydrogen fluoride in the presence of a fluorination catalyst to obtain mainly 1,1-difluoroethane,

(2) Separation of hydrogen fluoride, 1,1-dichloroethane and 1-chloro-1-fluoroethane and the separated compounds from the product containing 1,1-difluoroethane obtained in step (1) loop into the reaction step, and

(3) Hydrogen chloride and 1,1-difluoroethane are separated by distillation from the 1,1-difluoroethane-containing product obtained in step (1).

Step (1) may employ a method of performing a fluorination reaction between a starting material (such as 1,1-dichloroethane) and hydrogen fluoride in the presence of a fluorination catalyst to obtain crude 1,1-difluoroethane. The fluorination catalyst is preferably a supported or bulk catalyst mainly comprising trivalent chromium oxide.

In step (2), the product containing 1,1-difluoroethane obtained in step (1) is preferably introduced into the first distillation column, from which hydrogen fluoride, 1,1-difluoroethane, The overhead products (mainly hydrogen chloride and 1,1-difluoroethane) are separated from chloroethane and 1-chloro-1-fluoroethane, and the bottoms are recycled to the reaction step.

In step (3), it is preferable to introduce the product containing 1,1-difluoroethane obtained in step (1) into the first distillation column, and recover hydrogen chloride and 1,1-difluoroethane as the overhead product. Alkanes, these overhead products are introduced into the second distillation column, hydrogen chloride is mainly distilled out from the top, and 1,1-difluoroethane is mainly distilled out from the bottom, and then the above-mentioned purification method is carried out.

More preferably, the acid content (mainly hydrogen fluoride) of the azeotropic fraction contained mainly in 1,1-difluoroethane which is the bottom product of the second distillation column in step (3) is treated with an aqueous alkali solution, water etc. washing, and still more preferably, a dehydration step is provided after the washing, after which the above-mentioned purification method is carried out.

As described above, the purified 1,1-difluoroethane had a purity of 99.99% by volume. In particular, the water content is ≤ 5 vol ppm, and the hydrogen fluoride content (acid content) is ≤ 2 vol ppm.

The content of impurities contained in 1,1-difluoroethane can be measured by gas chromatography (GC) using the TCD method or FID method or by gas chromatography-mass spectrometry (GC-MS). Also, the acid content can be measured by ion chromatography, and the water content can be measured by the Karl Fischer method or the like.

High-purity 1,1-difluoroethane can be used as a refrigerant, in addition, the mixed gas of 1,1-difluoroethane and inert gas (such as He, N ₂ , Ar), HCl, O ₂ , H ₂ etc. It can be used as an etching gas in an etching step in a method of producing a semiconductor device. In the method of producing semiconductor devices such as LSI, LFT, and organic EL, a thin or thick film is formed by a CVD method, a sputtering method, or a vapor deposition method, and then etched to form a circuit pattern. During etching, the above-mentioned 1,1- Difluoroethane gas can be used as the etching gas. Etching using 1,1-difluoroethane can be performed under various dry etching conditions, such as plasma etching and microwave etching.

The method for purifying 1,1-difluoroethane of the present invention is characterized in that crude 1,1, 1-Difluoroethane is contacted with the fluorination catalyst in a gas phase state to reduce the content of unsaturated compounds each having two carbon atoms in the molecule.

The production method of 1,1-difluoroethane of the present invention includes the following two methods.

The first method is a method comprising the following steps. That is, (1) 1,1-dichloroethane is reacted with hydrogen fluoride in the presence of, for example, a fluorination catalyst mainly comprising trivalent chromium oxide at a reaction temperature of 150 to 350°C to obtain a compound mainly containing 1,1 - Products of difluoroethane. The obtained product contains the target 1,1-difluoroethane and additionally contains hydrogen chloride, unreacted hydrogen fluoride, 1,1-dichloroethane, 1-chloro-1-fluoroethane and impurities, such as each having two unsaturated or saturated compounds with carbon atoms. (2) introducing the product mainly containing 1,1-difluoroethane obtained in step (1) into a first distillation column, in the first distillation column, mainly separating hydrogen chloride belonging to a low-boiling point fraction from the top, and recycled for another use; separation and discharge from a stage above the middle of a distillation column containing mainly 1,1-difluoroethane and containing a small amount of hydrogen fluoride and at least a portion of saturated or unsaturated compounds each having two carbon atoms and the main separation and discharge of hydrogen fluoride, 1,1-dichloroethane and 1-chloro-1-fluoroethane belonging to the high boiling point fraction from the bottom, recycling to the reaction step and recycling. (3) The side draw (crude 1,1-difluoroethane) separated and discharged in step (2) contains a small amount of hydrogen fluoride and unsaturated compounds each having two carbon atoms as impurities. Among these compounds, as described above, there are compounds that are difficult to separate by known distillation operations, and therefore, the fluorination reaction is carried out in the presence of a fluorination catalyst in a gas phase state in order to separate the different impurities each having two carbon atoms that are impurities. Saturated compounds are transformed into saturated compounds. The total amount of unsaturated compounds each having two carbon atoms in the molecule belonging to the impurities contained in the crude 1,1-difluoroethane is preferably ≦1% by volume, more preferably ≦0.5% by volume. If the total amount of unsaturated compounds exceeds 1% by volume, it is not beneficial because a large reactor, high reaction temperature and the like are required. In crude 1,1-difluoroethane, hydrogen chloride is frequently contained, but the hydrogen chloride content is preferably ≦1% by volume. The fluorination catalyst to be contacted with crude 1,1-difluoroethane is preferably a catalyst belonging to a metal compound belonging to Groups 1B, 2A, 2B, 4B, 5A, 5B, 6A, 7A and 8 of the Periodic Table, and which The metal compound contains at least one element selected from Cu, Mg, Zn, Pb, Cr, Al, In, Bi, Co and Ni. For example, the catalyst is preferably (i) a supported or bulk catalyst mainly comprising trivalent chromium oxide or (ii) comprising Cr and at least one member selected from the group consisting of Cu, Mg, Zn, Pb, Al, In, Bi, Co and Ni Supported catalysts of the elements in . As the raw material of this catalyst, these metals and their oxides or salts can be used.

Supports that can be used to support the catalyst are alumina, fluorinated alumina or activated carbon.

As for (i) preparation of a catalyst mainly comprising trivalent chromium oxide, for example, an alkaline substance such as ammonia is added dropwise to an aqueous solution of a metal salt of chromium to precipitate chromium hydroxide, the precipitate is washed, filtered and dried, and The resulting chromium hydroxide is shaped and then heat-treated in the presence of an inert gas such as nitrogen, whereby the catalyst can be obtained. In the preliminary stage before being used in the reaction, the obtained catalyst is preferably subjected to a fluorination treatment (activation of the catalyst), for example, with hydrogen fluoride, which is a known method. The temperature of contacting with the catalyst is preferably 120-350°C, more preferably 150-250°C. If the contact temperature exceeds 350°C, this disadvantageously shortens the life of the catalyst or causes an increase in the kind or amount of by-products and the like. The molar ratio of hydrogen fluoride to unsaturated compound is preferably ≧1, hydrogen fluoride can also be newly added and reacted.

The second method for producing 1,1-difluoroethane is a method comprising the following steps. That is, (1) reacting 1,1-dichloroethane with hydrogen fluoride in the presence of, for example, a fluorination catalyst mainly containing trivalent chromium oxide at a reaction temperature of 150 to 350° C. to obtain a compound mainly containing 1,1 - Products of difluoroethane. The obtained product contains target 1,1-difluoroethane and additionally contains unreacted hydrogen fluoride, hydrogen chloride, 1,1-dichloroethane, 1-chloro-1-fluoroethane and impurities such as each having two Unsaturated or saturated compounds of carbon atoms. (2) The product mainly containing 1,1-difluoroethane obtained in step (1) is introduced into the first distillation column, and in the first distillation column, hydrogen chloride is mainly separated and discharged from the top, and recycled For other purposes, and mainly to separate and discharge from the bottom 1,1-difluoroethane, hydrogen fluoride, 1,1-dichloroethane and 1-chloro-1-fluoroethane and as impurities each with two carbon Atoms of unsaturated or saturated compounds. (3) The bottom fraction obtained in the step (2) is introduced into the second distillation column, and crude 1,1-distillate mainly containing a small amount of hydrogen fluoride and unsaturated compounds each having two carbon atoms is separated and discharged from the top. Fluoroethane, mainly hydrogen fluoride, 1,1-dichloroethane and 1-chloro-1-fluoroethane are separated and discharged from the bottom and recycled to the reaction step (1). (4) The overhead fraction obtained in step (3) is subjected to fluorination treatment (purification) by using the same operation and conditions as in the above-mentioned first method. (5) The reactant obtained in step (4) contains unreacted hydrogen fluoride, therefore, hydrogen fluoride must be recovered or removed from the reactant. Hydrogen fluoride is preferably recovered by a method such as using water, or preferably removed by a method such as bringing it into contact with an aqueous alkali solution or a cleaning agent. When the amount of unreacted hydrogen fluoride is large, it is preferably recovered with water and recycled; when the amount is small, it is removed by contacting with an aqueous alkali solution or a cleaning agent. The scavenger is preferably, for example, a scavenger comprising a carbonaceous solid material and at least one member selected from the group consisting of alkali metal compounds, alkaline earth metal compounds, alkali metal salts of aluminate, and tetraalkylammonium salts. After removal of hydrogen fluoride, the reactants mainly comprising 1,1-difluoroethane are contacted, for example, with a dehydrating agent such as zeolite, and then introduced into a purification step in which low-boiling components (for example, oxygen, nitrogen and carbon dioxide) are separated, followed by High-boiling components (for example, 1-chloro-1-fluoroethane which is a reaction product) are removed, and high-purity 1,1-difluoroethane is recovered.

The present invention is described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

Example 1

Preparation example of crude 1,1-difluoroethane (raw material example 1)

Introduce 1,1-dichloroethane and hydrogen fluoride into a reactor filled with a catalyst (mainly containing trivalent chromium oxide), and react at a temperature of 290°C to produce mainly 1,1-difluoroethane, hydrogen chloride and unreacted hydrogen fluoride gas. Then, hydrogen fluoride and hydrogen chloride are removed by distillation or the like to obtain crude 1,1-difluoroethane.

The obtained crude 1,1-difluoroethane was analyzed by gas chromatography and found to have the following composition:

CH ₃ CHF ₂ 99.9461 CH ₂ =CH ₂ 0.0018

CH ₂ =CHF 0.0143 CH ₃ CHClF 0.0013

CH ₂ =CHCl 0.0261 CH ₃ CHClF 0.0089

CH ₂ =CCl ₂ 0.0012 CH ₃ CHCl ₂ 0.0003

(Unit: volume %)

Also, in the obtained crude 1,1-difluoroethane, the water content was 25 vol ppm and the hydrogen fluoride content was 6 vol ppm.

Example 2

Preparation example of crude 1,1-difluoroethane (raw material example 2)

The crude 1,1-difluoroethane obtained in Example 1 (Material Example 1) was further distilled according to a known method to obtain crude 1,1-difluoroethane.

The obtained crude 1,1-difluoroethane was analyzed by gas chromatography and found to have the following composition:

CH ₃ CHF ₂ 99.9666 CH ₂ =CH ₂ 0.0006

CH ₂ =CHF 0.0083 CH ₃ CHClF 0.0011

CH ₂ =CHCl 0.0178 CH ₃ CHClF 0.0052

CH ₂ =CCl ₂ 0.0004

(Unit: volume %)

Also, in the crude 1,1-difluoroethane obtained, the water content was 23 vol ppm and the hydrogen fluoride content was 6 vol ppm.

Example 3

Zeolite [Molecular Sieve 5A (manufactured by Union Showa K.K., average pore diameter: 4.2 angstroms, Si/Al ratio=1.0)] (20 g) was filled in a 200 ml volume stainless steel measuring cylinder, and vacuum-dried. Then, about 80 g of crude 1,1-difluoroethane of Raw Material Example 1 was filled while cooling the graduated cylinder and stirring occasionally while maintaining the temperature at -10°C. After about 20 hours, the liquid fraction was analyzed by gas chromatography and had the following composition:

CH ₃ CHF ₂ 99.9925 CH ₂ =CH ₂ 0.0001

CH ₂ =CHF 0.0003 CH ₃ CHClF 0.0007

CH ₂ =CHCl 0.0021 CH ₃ CHClF 0.0035

CH ₂ =CCl ₂ 0.0007 CH ₃ CHCl ₂ 0.0001

(Unit: volume %)

Also, the water content in 1,1-difluoroethane obtained after purification was analyzed by the Karl Fischer method (water content analyzer), the result was 3 vol ppm, and the hydrogen fluoride content was measured by ion chromatography, the result was 1volppm.

Example 4

A carbonaceous adsorbent [molecular sieve separation carbon 4A (manufactured by Takeda Chemical Industries, Ltd., average pore diameter: 4 angstroms)] (20 g) was filled in a 200 ml volume stainless steel measuring cylinder, and vacuum-dried. Then, approximately 80 g of crude 1,1-difluoroethane of Raw Material Example 1 was filled while cooling the graduated cylinder and stirring occasionally while maintaining the temperature at -20°C. After about 18 hours, the liquid fraction was analyzed by gas chromatography and found to have the following composition:

CH ₃ CHF ₂ 99.9975 CH ₂ =CH ₂ 0.0001

CH ₂ =CHF 0.0005 CH ₃ CHClF 0.0002

CH ₂ =CHCl 0.0011 CH ₃ CHClF 0.0004

CH ₂ =CCl ₂ 0.0001 CH ₃ CHCl ₂ 0.0001

(Unit: volume %)

Example 5

The zeolite [molecular sieve 5A] (15 g) used in Example 3 was mixed with 15 g of the carbonaceous adsorbent [molecular sieve separation carbon 4A] used in Example 4, and the mixture was filled in a stainless steel measuring cylinder with a volume of 200 ml. , and vacuum dried. Then, about 100 g of crude 1,1-difluoroethane of Raw Material Example 2 was filled while cooling the graduated cylinder, and stirred occasionally while maintaining the temperature at 10°C. After about 20 hours, the liquid fraction was analyzed by gas chromatography and had the following composition:

CH ₃ CHF ₂ 99.9984 CH ₂ =CH ₂ 0.0001

CH ₂ =CHF 0.0003 CH ₃ CHClF 0.0002

CH ₂ =CHCl 0.0005 CH ₃ CHClF 0.0004

CH ₂ =CCl ₂ 0.0001

(Unit: volume %)

Also, in 1,1-difluoroethane obtained after purification, the water content was 4 vol ppm and the hydrogen fluoride content was 1 vol ppm.

Example 6

Zeolite [Molecular Sieve 4A (manufactured by Union Showa K.K., average pore diameter: 3.5 angstroms, Si/Al ratio=1.0)] (20 g) was filled in a 200 ml volume stainless steel measuring cylinder, and vacuum-dried. Then, approximately 80 g of crude 1,1-difluoroethane of Raw Material Example 2 was filled while cooling the graduated cylinder and stirring occasionally while maintaining the temperature at 10°C. After about 20 hours, the liquid fraction was analyzed by gas chromatography and had the following composition:

CH ₃ CHF ₂ 99.9911 CH ₂ =CH ₂ 0.0002

CH ₂ =CHF 0.0011 CH ₃ CHClF 0.0010

CH ₂ =CHCl 0.0032 CH ₃ CHClF 0.0032

CH ₂ =CCl ₂ 0.0002

(Unit: volume %)

Comparative example 1

Zeolite [Molecular Sieve 13X (manufactured by Union Showa K.K., average pore diameter: 10 angstroms, Si/Al ratio=1.2)] (20 g) was filled in a 200 ml volume stainless steel measuring cylinder, and vacuum-dried. Then, approximately 80 g of crude 1,1-difluoroethane of Raw Material Example 2 was filled while cooling the graduated cylinder and stirring occasionally while maintaining the temperature at 10°C. After about 20 hours, the liquid fraction was analyzed by gas chromatography and had the following composition:

CH ₃ CHF ₂ 99.9711 CH ₂ =CH ₂ 0.0006

CH ₂ =CHF 0.0077 CH ₃ CHClF 0.0009

CH ₂ =CHCl 0.0146 CH ₃ CHClF 0.0048

CH ₂ =CCl ₂ 0.0003

(Unit: volume %)

From these results, it can be seen that even when the Si/Al ratio is ≤ 2.0, impurities cannot be selectively adsorbed and removed if the average pore diameter of the zeolite exceeds 6 angstroms.

Comparative example 2

Activated carbon [Granular Shirosagi KL (manufactured by Takeda Chemical Industries, Ltd., average pore diameter: 35 angstroms)] (20 g) was filled in a measuring cylinder made of stainless steel with a volume of 200 ml, and vacuum-dried. Then, approximately 80 g of crude 1,1-difluoroethane of Raw Material Example 2 was filled while cooling the graduated cylinder and stirring occasionally while maintaining the temperature at 10°C. After about 20 hours, the liquid fraction was analyzed by gas chromatography and had the following composition:

CH ₃ CHF ₂ 99.9694 CH ₂ =CH ₂ 0.0006

CH ₂ =CHF 0.0081 CH ₃ CHClF 0.0008

CH ₂ =CHCl 0.0166 CH ₃ CHClF 0.0044

CH ₂ =CCl ₂ 0.0001

(Unit: volume %)

From these results, it can be seen that when activated carbon with a large pore size is used, impurities cannot be selectively adsorbed and removed.

Example 7

Preparation example of crude 1,1-difluoroethane (raw material example 3)

1,1-Dichloroethane and hydrogen fluoride were introduced into a reactor made of Inconel filled with a catalyst (mainly containing trivalent chromium oxide), and reacted at a reaction temperature of 200° C. The resulting reaction gas mainly comprising 1,1-difluoroethane, hydrogen chloride and unreacted hydrogen fluoride is introduced into the first distillation column, hydrogen chloride belonging to the low-boiling fraction is mainly separated from the top, mainly comprising crude 1,1-difluoroethane The side draw is separated and withdrawn from the stage above the middle of the distillation column. The resulting crude 1,1-difluoroethane has the following composition:

CH ₃ CHF ₂ 99.1938 CH ₂ =CH ₂ 0.0004

CH ₂ =CHF 0.0019 CH ₂ =CCIF 0.0005

CH ₂ =CHCl 0.0018 CH ₃ CHClF 0.0002

CH ₃ CH ₂ Cl 0.0002 CH ₂ =CCl ₂ 0.0004

HCl 0.2188 HF 0.5820

Unit: volume %

Example 8

Preparation example of crude 1,1-difluoroethane (raw material example 4)

1,1-Dichloroethane and hydrogen fluoride were introduced into a reactor made of Inconel filled with a catalyst (mainly containing trivalent chromium oxide), and reacted at a reaction temperature of 250° C. The resulting reaction gas mainly containing 1,1-difluoroethane, hydrogen chloride and unreacted hydrogen fluoride is introduced into the first distillation column, hydrogen chloride belonging to the low-boiling fraction is mainly separated from the top, and hydrogen fluoride, 1,1-difluoroethane , 1,1-dichloroethane and 1-chloro-1-fluoroethane are mainly separated from the bottom and introduced into the second distillation column. In the second distillation column, crude 1,1-difluoroethane, mainly comprising 1,1-difluoroethane, is obtained from the top, while hydrogen fluoride, 1,1-dichloroethane and 1-chloro-fluoroethane Mainly separated from the bottom and recycled to the above reaction step. The resulting crude 1,1-difluoroethane had the following composition.

CH ₃ CHF ₂ 99.7098 CH ₂ =CH ₂ 0.0002

CH ₂ =CHF 0.0011 CH ₂ =CCIF 0.0010

CH ₂ =CHCl 0.0008 CH ₃ CHClF 0.0002

CH ₃ CH ₂ Cl 0.0001 CH ₂ =CCl ₂ 0.0002

HCl Trace HF 0.2866

Unit: volume %

Example 9

The preparation embodiment of catalyst (catalyst embodiment 1)

Pure water (0.6L) was added to a 10L container, stirred, and dropped by adding 452g of Cr(NO ₃ ) ₃ .9H ₂ O and 42g of In(NO ₃ ) ₃ .nH ₂ O ( n is approximately 5) a solution obtained by dissolving in 1.2 L of pure water and 0.31 L of 28% ammonia water while controlling the flow rates of the two aqueous solutions so that the pH of the reaction solution is 7.5-8.5. The resulting slurry was separated by filtration, and the solid matter separated by filtration was thoroughly washed with pure water, followed by drying at 120° C. for 12 hours. The dried solid material is ground, mixed with graphite, and shaped into pellets by a tablet press.

The produced pellets were baked at 400° C. for 4 hours in a nitrogen stream to obtain a catalyst precursor. This catalyst precursor was charged into a reactor manufactured by Inconel, and a catalyst was prepared by performing a fluorination treatment (catalyst activation) at 350° C. using hydrogen fluoride.

Example 10

The preparation embodiment of catalyst (catalyst embodiment 2)

Chromium chloride (CrCl ₃ ·6H ₂ O) (191.5 g) was added to 132 mL of pure water, and dissolved by heating at 70-80° C. with a water bath. After cooling the resulting solution to room temperature, 400 g of activated alumina (NST-7, produced by Nikki-Universal Co., Ltd.) was added so that the entire amount of the catalyst solution was adsorbed into the alumina. The alumina wetted with the catalyst solution was dried in a water bath at 90° C., thereby being dehumidified. The dehumidified catalyst was dried at 110° C. for 3 hours in a hot air drier with air circulation, the dried catalyst was charged into a container made of SUS, and the temperature was raised to 400° C. under air circulation to produce a catalyst precursor. Thereafter, fluorination treatment of the catalyst (activation of the catalyst) was performed by using the same procedure and conditions as in Example 6 to prepare a catalyst.

Example 11

The preparation embodiment of catalyst (catalyst embodiment 3)

The catalyst was prepared by the same procedures and operations as in Example 10, except that 16.6 g of zinc chloride (ZnCl ₂ ) was added as the second component in Example 10.

Example 12

The catalyzer (80mL) that obtains in embodiment 9 (catalyst embodiment 1) is packed in the Inconel 600 type reactor of internal diameter 1 inch and length 1 meter, and reactor temperature is raised while feeding nitrogen To 160°C, add the crude 1,1-difluoroethane obtained in Example 7 (raw material example 3) at a flow rate of 10NL/h, stop the supply of nitrogen, and after 2 hours, the reactor outlet gas was sprayed with an aqueous alkali solution The acid content was removed and analyzed by gas chromatography. As a result, the gas was found to have the following composition:

CH ₃ CHF ₂ 99.9966 CH ₂ =CH ₂ 0.0001

CH ₂ =CHF 0.0001 CH ₃ =CCIF 0.0001

CH ₂ =CHCl Trace CH ₃ CHClF 0.0002

CH ₃ CH ₂ Cl 0.0005 CH ₂ = Trace amount of CCl ₂

CH ₃ CClF ₂ 0.0004 CH ₃ CHClF 0.0017

_{CH3CCl2F 0.0003}

Unit: volume %

From these results, it can be seen that about 94% of unsaturated compounds each having two carbon atoms were converted into saturated compounds.

Example 13

In an Inconel 600 type reactor with an internal diameter of 1 inch and a length of 1 meter, the catalyst (100 mL) obtained in Example 10 (Catalyst Example 2) was charged, and the reactor temperature was raised while nitrogen was introduced To 200°C, add the crude 1,1-difluoroethane obtained in Example 8 (raw material example 4) at a flow rate of 10NL/h, and simultaneously add hydrogen fluoride at a rate of 2NL/hr, stop nitrogen supply, and After hours, the outlet gas was stripped of its acid content with an aqueous base solution and then analyzed by gas chromatography. As a result, the gas was found to have the following composition:

CH ₃ CHF ₂ 99.9984 CH ₂ =CHF 0.0001

CH ₂ =CHCl 0.0001 CH ₃ CHClF 0.0001

CH ₃ CH ₂ Cl 0.0003 CH ₃ CCIF ₂ 0.0009

_{CH3CCl2F 0.0001}

Unit: Volume %

From these results it can be seen that approximately 94% of the unsaturated compounds were converted to saturated compounds.

After passing through the aqueous alkali solution, the above gas is dehydrated with zeolite, collected in the pressure vessel while cooling, and introduced into the third distillation tower, and cut off the low boiling point fraction from the top of the tower, and the bottom fraction is introduced into the fourth distillation tower, and then from 1,1-difluoroethane was recovered from the top of the tower and analyzed by gas chromatography. As a result, the gas was found to have a purity of ≥99.999% by volume and an unsaturated compound content of ≤2 vol ppm.

Example 14

A reaction was performed by employing the same operation and conditions as in Example 13, except that 100 mL of the catalyst obtained in Example 11 (Catalyst Example 3) was filled. The outlet gas was stripped of its acid content with an aqueous alkali solution and then analyzed by gas chromatography. As a result, the gas was found to have the following composition:

CH ₃ CHF ₂ 99.9985 CH ₂ =CHF 0.0001

CH ₂ =CHCl 0.0002 CH ₃ CHClF 0.0001

CH ₃ CH ₂ Cl 0.0002 CH ₃ CCIF ₂ 0.0008

_{CH3CCl2F 0.0001}

Unit: volume %

Industrial applicability

The present invention can produce high-purity 1,1-difluoroethane, which can be industrially advantageously used as a low-temperature refrigerant or as an etching gas.

Claims (9)

1. A method of purifying 1,1-difluoroethane, which comprises making a compound containing chlorine selected from unsaturated compounds each having two carbon atoms in the molecule and saturated chlorine-containing compounds each having two carbon atoms in the molecule Crude 1,1-difluoroethane of at least one of the compounds comprises zeolites having an average pore diameter of 3-6 angstroms and a silica/alumina ratio of ≤ 2.0 and/or zeolite having an average pore diameter of 3.5-6 angstroms Adsorbent contacting of the carbonaceous adsorbent to reduce the content of said compounds contained as impurities in the crude 1,1-difluoroethane. 2. The method for purifying 1,1-difluoroethane as claimed in claim 1, wherein the unsaturated compound having two carbon atoms in the molecule is at least one selected from the group consisting of ethylene, vinyl fluoride, vinyl chloride and difluoroethylene Compounds in vinyl chloride. 3. The method for purifying 1,1-difluoroethane as claimed in claim 1, wherein the saturated chlorine-containing compound having two carbon atoms in the molecule is at least one selected from dichloroethane, 1-chloro- Compounds in 1-fluoroethane and 2-chloro-1,1,1,2-tetrafluoroethane. 4. The method for purifying 1,1-difluoroethane as claimed in any one of claims 1-3, wherein the total content of said compounds contained as impurities in crude 1,1-difluoroethane is equal to or less than 0.1% by volume. 5. The method for purifying 1,1-difluoroethane according to any one of claims 1-4, wherein the pressure at which the crude 1,1-difluoroethane contacts the adsorbent is equal to or lower than 1 MPa . 6. The method for purifying 1,1-difluoroethane as claimed in any one of claims 1 to 5, wherein the total amount of said compounds contained as impurities in the purified 1,1-difluoroethane is The content is equal to or less than 100vol ppm. 7. The method for purifying 1,1-difluoroethane as claimed in any one of claims 1-6, wherein each of the impurities contained in the purified 1,1-difluoroethane has The total content of unsaturated compounds with two carbon atoms is equal to or less than 50 vol ppm. 8. The method for purifying 1,1-difluoroethane as claimed in any one of claims 1-7, wherein each of the impurities contained in the purified 1,1-difluoroethane has The total content of saturated chlorine-containing compounds with two carbon atoms is equal to or less than 50 vol ppm. 9. The method for purifying 1,1-difluoroethane as claimed in any one of claims 1-8, wherein crude 1,1-difluoroethane is passed through a method comprising the following steps (1)-(3) to get: (1) reacting 1,1-dichloroethane with hydrogen fluoride in the presence of a fluorination catalyst to obtain mainly 1,1-difluoroethane, (2) separating hydrogen fluoride, 1,1-dichloroethane and 1-chloro-1-fluoroethane from the product containing 1,1-difluoroethane obtained in step (1) and separating the separated The compound is recycled to the reaction step, and (3) Hydrogen chloride and 1,1-difluoroethane are separated by distillation from the 1,1-difluoroethane-containing product obtained in step (1).